Hip fractures, wherein the femur is fractured one or more times in the area of the intertrochanteric region of the femur, or immediately subjacent the head, are fairly common. A great many devices have been proposed for the reduction of fractures of this type. While many of these devices have found application and have advantages relative one to another, there remain some problems and areas of continuing concern.
Such reduction devices consist, basically, of an elongate lag screw which is threaded on one end to be threadably received in the head of the femur, and is secured to a plate such that when the lag screw is tightened, the head of the femur is forcibly compressed at the fracture line to the remainder of the femur. Devices of this type, generally, are described in U.S. Pat. Nos. 2,526,959 and 3,554,193.
It has also been recognized that various adjustment features are important in treating certain femoral fractures. In general, fastener devices with such adjustment features employ a guide sleeve which is imbedded in one bone segment, such as the upper segment of the femur, in order to receive and adjustably hold one end of an axially elongated shaft, e.g. a lag screw, which extends through both fractured bone segments, with the end of the shaft opposite the guide sleeve being provided with structure for securing the shaft to the head of the femur. Because of absorption occurring during the healing process, it has been necessary, in some instances, to accommodate a certain amount of telescoping movement between the shaft and the guide sleeve. Clasping devices within this class generally are described in the U.S. Pat. Nos. 3,996,931 and 4,095,591.
Functionally, some of these devices perform quite satisfactorily for many fractures of the femur but limit the sequence in which the components may be implanted thereby limiting the flexibility of a surgeon. Moreover, with some devices used to angularly lock the lag screw, locking is achieved by torquing two components together. In these systems, special instruments may be needed to ensure application of the proper amount of torque to achieve the desired angular lock.
What is needed, therefore, is a bone fixation assembly that that allows for different sequencing of component implantation.
What is further needed is a bone fixation assembly that allows a lag screw to be angularly locked to a side plate in a plate first implantation as well as a lag screw first implantation.
What is also needed is a bone fixation assembly that provides a reliable indication of achieving an angular lock between a lag screw and a bone plate.
What is needed is a bone fixation assembly that maintains a reliable angular lock between a lag screw and a bone plate.